Target assembly for cathode-ray tubes



March 27 1951 G. LEVY 2,546,828

TARGET ASSEMBLY FOR CATHODE-RAY TUBES Filed Feb. 17, 1950 I N VEN TOR.60am 1 5 151/ y nu M Patented Mar. 27, 1951 UNITED STATES PATENT OFFICETARGET ASSEMBLY FOR CATHODE-RAY TUBES Application February 17, 1950,Serial No. 144,627

1 Claim. 1 This invention relates to electron tubes and moreparticularly to methods and means for supporting large area targets orscreens Within a cathode-ray tube and the like.

A principal object of the invention is to pro vide a novel supportarrangement for fluorescent screens, target. electrodes and the like,whereby the screen or target can be prepared and processed. prior tomounting it within the cathoderay tube bulb and can thereafter bepermanently attached within the bulb without using wires or leads sealedthrough the bulb wall.

A further feature of the invention relates to an improved arrangementfor accurately locating and supporting a plate-like screen or target inthe enlarged end portion of a cathode-ray tube.

' A further feature relates to the novel organization, arrangement andrelative location and interconnection of parts which cooperate toprovide an improved target supporting arrangement for cathode-ray tubes.

Other features and advantages not particularly enumerated, will beapparent after a consideration of the following detailed descriptionsand the appended claims.

In certain kinds of cathode-ray tubes, it is important that a relativelylarge fiat plate-like screen or target be mounted within the tubeenvelope adjacent the enlarged flattened end of the bulb. Two differentprocedures have been used heretofore. In one procedure, the screenortarget is first located within the bulb and is then coated orprocessed with the desired material, for example, fluorescent material,ionic screen material, secondary emission material and the like. 'Thisusually requires that the screen or target be rigidly attached to metaltabs or inserts which are sealed through the wall of the bulb. Certaindifficulties have been encountered with such procedure particularly asit is diflicult to confine the coating entirely to the target. Thealternative procedure has been to prepare or coat the screen or targetbefore it is assembled into the bulb. This however has usually requiredthat the target or screen be supported on metal rods or wires which aresealed through or anchored in the wall of the tube. For example, in onearrangement, the screen or target is supported on a rod or wire which issealed through the press or neck of the tube, and when the target hasbeen processed the enlarged portion of the bulb is assembled over thetarget and two parts of the bulb are welded or spliced together.However, even with this arrangement, the target being located at oneextreme end of the tube and being supported by relatively long wiresadjacent the opposite end of the tube, is subject to undesirablemovement or vibration and itis some times difiicult to locate the targetwith uniform accuracy as regards its closely spaced relation :to theflattened end of the tube wall. Furthermore, in certain types oftargets, for example those used in ionic crystal. screen tubes and thelike, it is highly important that the target be held out of direct heatconductive contact with the tube wall. The present invention provides anarrangement for meeting all the above-noted difficulties.

There is shown in the drawing any well-known cathode-ray tube bulb orenvelope, comprising the usual constricted neck portion 1, which isjointed to a flared portion 2, which latter portion terminates in theenlarged bulbous end portion rdinarily, the end portion 3 is closed by aflattened wall 4. In accordance with one phase of the invention, thesection 3 of the bulb is a separate unit from the section 2, and isarranged to be sealed thereto after mounting and anchoring of the targetor screen electrode. The target 'or screen electrode 5 may comprise athin plate of suitable material, for example a circular or rectangulardisc of metal of the required thin cross section. In some cases, thetarget 5 may consist of a thin disc or plate of light transparentmaterial such as glass or mica which is coated with any of thewell-known fluorescent screen or ionic crystal screen materials. It isalso desirable in devices of this type to locate the screen or target 5as close as possible to the flattened end wall 3 of the tube but withoutdirect heat conductive contact therewith.

Preferably, although not necessarily, the screen or target 5 has aflange or rim 6 to which there are attached as by welding, fusing,soldering or the like, a series of line tungsten springy wires 1, 8, 9,for example of approximately .025 inch in diameter. At least four ofthese wires should be attached equally at spaced points around theflange three of these wires being shown in the drawing. The wires 7 and9 are preferably located diametrically opposite to each other, as is thewire 8 and the corresponding Wire (not Shown). Welded or otherwiserigidly united to the free end of each of the wires is a short length ofchromium-iron alloy wire Iii which is also welded to a chromium-ironalloy disc I i. Preferably, the .disc I I and wire it are made of analloy which may have the same temperature-expansion characteristics asthe glass of section 3, for example the alloy sold under the trade-nameDriver Harris Co. Alloy #14. Preferably this section 3 is made of leadglass having a relatively high melting point. The disc 10 has integrallyfastened thereto a bead l2 also of lead glass.

t will be observed that by this arrangement of parts, the tungsten wires1, 8 and 9, because of their natural'springiness, tend to hold theglassbeaded discs i outwardly to the dotted line position. In order toassemble the parts, the target 5, carrying its four tungsten wires andtheir respective glass beaded discs, is inserted into the lead glassbulb section 3 to the desired distance until the target is closelyspaced from the face 4. It will be observed that because of thespringiness of the tungsten wires, when the target is inserted to theproper position, it is retained in that position because of the outwardpressure of the glass beaded discs l against the inclined wall of thebulb section 3.

When the target has been thus located within the section 3, the latteris brought into abutting engagement with the corresponding section 2 ofthe bulb and the abutting area is subjected to the required'sealing heatfrom the usual torches ortne like. In accordance with one feature of theinvention, the tungsten wires 1, 8 and 9, etc. are of sufficient lengthso that when the target is properly located adjacent the wall 4, theglass beaded discs It are adjacent the end of section3 which abutsagainst the section 2. Consequently, the heat that is used to fuse thesection 2 and 3 together also causes suficient softening of the glassbeads i2 to cause them to fuse to the wall of section 3; Thus thetungsten wires serve the double nurpose of firmly holding the target inits accurate location during the joining of the .bulb sections 2 and 3,and also they exert considerable pressure radially outward against thewall of section 3 to facilitate fusion of the glass beads i2 to thewall'of sec;.ion 3 during the bulb splicing operation. Furthermore, withthis arrangement, the target 5 is completely electrically'insulated fromthe cathode-ray bulb which is'of importance in certain kinds ofcathode-ray-tubes. Various changes and modifications may be made in thedisclosed embodiment without de- 4 parting from the spirit and scope ofthe invention.

What is claimed is:

In combination, a cathode-ray tube having an enlarged bulb section whichis arranged to be sealed to the end of a corresponding flared sec tionof the cathode-ray tube, a screen member within the tube, means toanchor and locate said member in spaced relation to the inner surface ofthe end wall of said bulb section, the lastmentioned means comprising aseries of springy tungsten wires each terminating atone end in a glassbeaded metal alloy disc having substantially the same coefficient ofexpansion as the glass of the bulb, each wire being integrall attachedat its opposite end to the margin of said member and beingspring-pressed inwardly by engagement of the beaded end thereof with thewall of the bulb section, the glass bead on each wire being fused to theinternal side Wall surface only of said bulb section for thermally andelectrically insulating the screen member from the bulb section, saiddiscs on said wires being located adjacent the sealing region betweensaid flared section and said enlarged bulb section whereby the sealingheat for effecting-sealing of the two bulb sections simultaneouslycauses fusion of said glass beads to the wall of said bulb section.

- GUSTAVE LEVY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,934,821 Ptudenberg Nov. 14,1933 2,100,703 Schlesinger Nov. 30, 1937 2,123,957 Orth July 19, 19382,124,225 Batchelor July 19, 1938 2,195,444 Brett a Apr. 2, 19492,303,166 Laico Nov. 24, 1942 2,425,980 Baird Aug. '19, 1947 2,435,296SZegho .1 Feb. 3, 1948 2,448,476 Szegho Aug. 31, 1948 2,472,988Rosenthal June 14, 1949 2,489,850 Baker 1 Nov. 29, 1949

